1. Field of the Invention
The present invention relates to a fan unit including a fan generating airflow.
2. Description of the Prior Art
A fan is incorporated in a water heater as disclosed in Japanese Patent Application Publication No. 8-178273, for example. The actual rotation speed of the fan is compared with a designated or target rotation speed of the fan for detection of a failure in the fan. When the actual rotation speed is significantly lower than the designated rotation speed, a failure, such as occlusion of a ventilation opening, deterioration of the fan, or the like, is detected in the fan.
A centrifugal fan is often utilized in a so-called notebook personal computer for cooling a central processing unit, CPU, for example. The inventors tried to detect occlusion of the ventilation opening of the centrifugal fan in the aforementioned manner. The inventors have practically examined the occlusion of a ventilation opening, namely the accumulation of dust in the ventilation opening. However, it has been confirmed that the aforementioned method cannot succeed in the detection of the occlusion of the ventilation opening.